A CVT is a uniform-motion transmission in which the ratio of the rotational speeds of the driving shaft and of the driven shaft, the transmission ratio, can assume an infinite number of values (stages) in a certain range. This may also include the standstill state or the rotational direction reversal of a shaft. The transmission of the movement takes place via a non-rigid coupling of components, the geometries of which determine the transmission action according to the lever principle. A change in transmission ratio is obtained by means of a change in said component geometries, which however at the same time cannot take place without a change in the geometries at the location of the component coupling.
Numerous freewheel devices for crank-type CVTs have, for this purpose, clamping bodies which are arranged between an inner ring, which is formed by a region of the drive output shaft, and an outer ring. Here, the surfaces of the outer ring and of the inner ring are coordinated with one another such that, in one direction of relative rotation between the inner ring and outer ring, the clamping bodies can block said rotation, such that the outer ring and the inner ring are rotated together. In the other direction of relative rotation between the outer ring and the inner ring, no blocking action is effected by the clamping bodies. The individual clamping bodies are loaded in the blocking direction, which may be realized by means of at least one spring element.
For example, documents DE 1814968 A, DE 6811650 B and DE 3233073 C2 disclose freewheel clutches having a multiplicity of tillable clamping bodies which are spaced apart from one another and which are inserted between an outer ring 1 and an inner ring, wherein the clamping bodies are guided in a cage and are preloaded or held by means of an encircling spring, which imparts an inward loading, in the engagement or functional engagement direction. A rectilinearly running groove for receiving the spring is formed through the center of the clamping bodies.
The springs may take the form of an annular band spring, an annular groove spring or a spiral spring (worm spring), which in the latter case engages into worm spring grooves of the clamping bodies.
Also known are clamping body freewheels without a cage, in which the guidance of the tiltable clamping bodies is realized, as in a cageless needle-roller bearing, at the center of the clamping bodies for example by means of a meandering spring, wherein the clamping bodies bear against one another.
It is a disadvantage that, in particular in the case of cageless freewheels, the clamping bodies can undesirably rotate about their own axes under highly dynamic conditions, and the clamping function is thereby impaired.